This invention relates to a disk brake pad wear warning device and, more particularly, to such a device particularly suitable for a vented disk brake.
It is often desirable that the car operator be informed of excessive brake pad wear prior to the occurrence of brake failure and/or brake damage and, therefore a variety of pad wear warning devices have been proposed.
A system in which, when the wear of a brake pad reaches its use limit, an elastic contactor is brought into contact with a rotating disk, as a result of which a sound is generated to indicate the wear of the pad, is disclosed in Japanese Patent Publication No. 43862-1974. In the warning device therein disclosed, as shown in FIG. 1, a spring member 108 is suspended above the disk. The upper portion of the spring member includes flange portions 109 and 110, the former being relatively large and the latter relatively small. The lower portion 113 of the spring member 108 includes a pair of hook portions 112 for engaging the small flanges 110 when the device is set. The flanges 109 abut the disk brake pad backing plates so that when excessive wear has occurred the flanges 109 and, consequently, the flanges 110 will be compressed together, thereby releasing the lower portion 113 to press against the outer periphery of the disk. Such an arrangement is unsuitable for use in a vented disk brake system for two reasons. First, when the lower portion 113 presses against the periphery of the disk, there is a danger that it will protrude too far into the recesses in the outer periphery of the disk to thereby be bent or otherwise damaged. Secondly, when excessve brake wear has occurred and the portion 113 has been released, a slight backward movement of the vehicle, such as may occur on an incline or when operating the vehicle in reverse, will cause the tip of the portion 113 to engage the inner wall of the disk groove into which it protrudes and the warning device will be destroyed as the portion 113 is forced to the right as viewed in FIG. 1.